The objective of this proposed research is to develop immunodiagnostic methods for detection of breast cancer. Using established methodologies, immune complexes are to be purified from the sera and effusions of breast cancer patients. Purified immune complexes will serve as immunogens for the production of hybridoma-derived monoclonal antibodies. Developed antibodies which exhibit specificity towards breast tumor cells will be utilized to construct immunoassays for detection of circulating antigen in both free and immune complexed forms. Patients with cancer of the breast and other tumor histotypes, as well as controls, will be evaluated for the presence of serum antigen. The ultimate goal of this proposal is to detect, by means of immunodiagnosis, the early, localized, breast tumor.